1. Field of the Invention
The present invention pertains to a tandem control and operating assembly for use in achieving a desired grade (including, without limitation, a precise final grade) on a variety of earth moving applications. More particularly, the present invention pertains to a tandem phasing hydraulic assembly for use in elevation and cross-slope tilt control on earth moving equipment, using a 2-D (two dimensional) or 3-D (three dimensional) machine control grading system.
2. Brief Description of the Related Art
Earth-moving projects can encompass a wide variety of excavating, trenching, boring, scraping, spreading and other tasks, which are performed in connection with road-building, infrastructure improvements, construction, mining and other activities. During earth-moving operations, a wide variety of equipment can be used for specific applications. Such equipment can include, without limitation, excavators, backhoes, bulldozers, loaders and motor graders.
One such earth-moving process is commonly referred to as “grading.” Grading is frequently used during construction operations in order to create a smooth base having a designed surface slope. The grading process is typically used in connection with many different earth-moving projects including, without limitation, construction or reconditioning of sports fields, planar and non-planar commercial parking areas, residential subdivisions, roadways, agricultural areas and the like. Design parameters such as water runoff, slope, compaction (typically for load-bearing capacity) and thicknesses of various material layers, represent important grading and site design criteria.
In most instances, such grading operations typically involve a combination of “cutting” (that is, removal of earth or other materials) and “filling” (that is, placement of earth or other materials) operations that are required in order to achieve a final grading plan. During grading operations, cut and fill quantities are preferably beneficially balanced in order to avoid inefficiencies associated with obtaining additional fill material or removing excess material.
During grading and other earth-moving operations, mobile equipment generally must be steered and/or otherwise guided within a particular jobsite, while the working components of such equipment (such as, for example, blades, buckets and/or ground-engaging tools) must be controlled through their respective ranges of motion. Such steering, guidance and control have historically been accomplished by human operators; such human operators typically require relatively high levels of skill, training and experience for achieving desired results piloting such earth-moving equipment.
More recently, three-dimensional machine controlled guidance systems have been developed in order to provide automated control of such earth moving equipment. Such machine controlled guidance technology can be used to reduce human control, thereby increasing earth-moving efficiency and overall job quality. In many instances, such technology utilizes a global positioning system (“GPS”), as well as other measurement control systems, in order to automatically guide and control equipment used to place, level and/or compact dirt and other materials.
So-called “fully automatic” three-dimensional machine controlled guidance systems permit automated operation of earth moving equipment, as well as the working components thereof, in order to conform to a predetermined site plan. Such site plan, typically created by an engineering or other design firm, can be imported into said three-dimensional machine controlled guidance system. Thereafter, said earth moving equipment and the associated working components can be automatically controlled and oriented in order to move dirt or other materials to match said predetermined site plan.
Generally, cutting edges of earth-moving equipment are positioned using fluid powered (typically hydraulic) drive cylinders. Such drive cylinders are used to move blades and other working components up and down, and to adjust vertical and horizontal angles of such blades and other components. With fully automatic three-dimensional machine controlled guidance systems, control fluid for such drive cylinders is directed to and from said cylinders using electrically actuated servo-type valves which, in turn, are controlled by a computer-driven operating system.
Onboard computers and operating software can utilize satellite GPS positioning information, as well as predetermined design data, in order to guide earth-moving equipment around a job site and automatically adjust positioning of working components of such equipment. Sonic and/or laser sensors can also be used to provide information, such as distance, elevation or proximity measurement, to said three-dimensional machine controlled guidance systems. Such information is provided to computer processor(s) which process such information and electronically control said servo valves which, in turn, control fluid powered drive cylinders. In this manner, cutting edge(s) of working components can be automatically moved or adjusted to match predetermined job parameters.
Unfortunately, conventional earth moving devices equipped with double action fluid powered drive cylinders suffer from some significant limitations. Such conventional cylinders typically include a relatively large number of moving parts that eventually wear or fail, including, but not limited to, pivot pins, bushings, bearings, hoses, and hydraulic fittings. Such failures generally give rise to costly down time and a frequent need for expensive and time consuming repairs.
Further, conventional double action drive cylinders are generally supplied with fluid from a common fluid supply conduit; such fluid passes through a flow divider that is designed to split such fluid flow volume in a desired proportion (frequently, 50/50) between multiple cylinders. However, when earth moving equipment is subjected to uneven loading, such divided fluid flow will typically take a path of least resistance, causing said fluid split to deviate from said desired proportion. As a result, such conventional fluid powered double action drive cylinders are especially prone to failure when installed on scrapers and/or other earth moving equipment exposed to uneven distribution of dirt or other earth material and, thus, uneven loading.
Thus, there is a need for a robust earth moving assembly equipped with fluid powered cylinders capable of providing consistency, accuracy and repeatability in operation. Said earth moving assembly should beneficially utilize less moving parts than conventional equipment, thereby providing for a more durable and effective solution to earth moving applications.